package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.Value;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);


    public <R, ID> R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) {
        //1.从redis查询商户缓存
        String key = keyPrefix + id;
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在, 直接返回
            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否是空值
        if (json != null) {
            //返回错误信息
            return null;
        }
        //4.不存在, 根据id查询数据库
        R r = dbFallback.apply(id);
        //5.不存在, 返回错误
        if (r == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }
        //6.存在, 写入Redis
        this.set(key, r, time, unit);
        //7.返回
        return r;
    }

    public <R, ID> R queryWithLogicalExpire(
            String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit){
        //1.从redis查询商户缓存
        String key = keyPrefix + id;
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(json)) {
            //3.不存在, 返回null
            return null;
        }
        //4.命中,需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())){
            //5.1未过期,直接返回店铺信息
            return r;
        }
        //5.2已过期,需要缓存重建
        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2判断是否获取锁成功
        if (isLock){
            //6.3成功,开启独立线程,实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入Redis
                    this.setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        //6.4返回过期的商铺信息
        return r;
    }

      public <R, ID> R  queryWithMutex(ID id, Function<ID, R> dbFallback,
                                       Class<R> type, String keyPrefix,Long time, TimeUnit unit){
        try {
            //1.从redis查询商户缓存
            String key = keyPrefix + id;
            String rJson = stringRedisTemplate.opsForValue().get(key);
            //2.判断是否存在
            if (StrUtil.isNotBlank(rJson)) {
                //3.存在, 直接返回
                return JSONUtil.toBean(rJson, type);
            }
            //判断命中的是否是空值
            if (rJson != null){
                //返回错误信息
                return null;
            }

            //4.实现缓存重建
            //4.1获取互斥锁
            boolean isLock = tryLock(LOCK_SHOP_KEY);
            //4.2判断是否获取成功
            if (!isLock){
                //4.3如果失败, 则休眠并重试
                Thread.sleep(50);
                return queryWithMutex(id, dbFallback, type, keyPrefix, time, unit);
            }

            //4.4成功, 根据id查询数据库
            R r = dbFallback.apply(id);
            //模拟重建的延迟
            Thread.sleep(50);
            //5.不存在, 返回错误
            if (r == null) {
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(key,"", CACHE_NULL_TTL, TimeUnit.MINUTES);
                //返回错误信息
                return null;
            }
            //6.存在, 写入Redis
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(r), time, unit);
            //8.返回
            return r;
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }finally {
            //7.释放互斥锁
            unlock(keyPrefix);
        }
    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }
}
